The present invention concerns an apparatus, for deploying an object or a load on the seabed, the object or the load being coupled to hoisting means, such as a hoisting wire in order to enable the object or the load to be lowered to the seabed from a vessel, the apparatus comprising a body having means for releasably securing the object or the load to the body and propulsion means for moving the body when submerged without using guide wires.
The present invention concerns a guiding, controlling and positioning system, used during the deployment and/or recovery of loads (packages) up to xc2x11000 tons on the sea bed, at great depth. Structurally, the system comprises a main module and a smaller counter module joined to each other by a frame.
Due to its functions, the system""s frame can be clamped directly to a load or alternatively to any hoisting means, hence securing the loads (packages) to be deployed. Equally, the system can release the said loads at any chosen time. The system also comprises propulsion- and moment control means, enabling it to control the behaviour of the load while being deployed through the entire water column.
Since oil and gas at sea can also be exploited by means of floating production platforms, such exploitation of oil- and gas fields requires that several heavy objects be deployed on the seabed, moreover, these objects have to be positioned on the seabed with a relatively high accuracy.
Due to the fact that nowadays oil exploration is being conducted at greater depth, achieving the required accuracy is increasingly more difficult. To achieve such an accuracy according to traditional methods, usually a crane vessel is used. The loads are lowered to the seabed by way of auxiliary, control wires either rigged to the same vessel and/or one or more auxiliary installation supports.
Using such methods is extremely expensive. The latter have been devised in order to control turning moments in installation aids induced primarily by changing current profiles but also by non-torque balanced wire ropes. By the same token, the aim is also to guide the load towards its final heading and within its required target area.
The object of the invention therefore is to devise a system and appropriate method by which loads (packages) will be deployed, controlled and positioned accurately on the seabed in a cheaper and faster manner than the conventional installation approaches.
This object, according to the present invention, is achieved. Thereby it is possible that the apparatus is provided with first and second propulsion means secured to the body, the first and second propulsion means being positioned at opposite sides of the means for releasebly securing the object or the load.
With this measures an anti-twist device is provided. Moreover with the thrusters the position of the apparatus, and so the load, with respect to the load can be adjusted and controlled.
According to the invention it is possible that, the apparatus is provided with means to adjust the distance between the first and second propulsion means.
Also it is possible that the first propulsion means are positioned in a first-module and that the second propulsion means are positioned in a second-module.
According to the present invention and in order to eradicate these traditional costs, the system is provided with a set of four thrusters working in pairs, each having a dedicated function, namely; a torque control function and a translation function.
These thrusters are mounted on each side of the system""s frame, two by two, in such a way as to achieve the above mentioned torque control by dedicating both lower thrusters to this torque control function and to achieve the translation control by dedicating both upper thrusters to this translation function.
Moreover, the second or counter module can move horizontally over a section of the frame, in order to improve torque control and to minimize stress cycles in the overall structure. It is understood that this frame comprises a hydraulically activated clamping system, ending in dedicated clamping adapters, provided with a high friction medium.
According to the invention it further possible that the propulsion means are provided in the form of thrusters.
As stated above it is possible that the first propulsion means are positioned in a first-module and that the second propulsion means are positioned in a second-module. The second-module could be attached to an arm, the length of the arm being adjustable.
According to a preferred embodiment of the invention, the first module is secured detachably to the apparatus.
According to the invention it is possible that the means for releasably securing a load comprises hydraulic jacks. Moreover the means for releasably securing a load in the apparatus could be provided with purposed designed adapters, the adapters being covered with a high friction medium.
In order to be able to achieve the required accuracy during deployments, it is preferred that the apparatus is provided with means adapted to transmit information in the direction of an object on the seabed, and with means to receive a reflection of the signal transmitted to the object, and a processor to compute the reflected information to establish the position of the apparatus with respect to the object. Also, the apparatus could be provided with a distance log.
The means for transmitting information could include sonar equipment, such as High Resolution Sonar Equipment. When the position of the load to be deployed with respect to the object on the seabed is determined, using the sonar equipment, the positioning of the load could be finalized using the distance log. So, it is possible to dissociate this final positioning activity from the surface support.
According to the present invention not only the apparatus but also a method for deploying an object or a load at the seabed is provided, the method being characterized in that the method comprises the steps of:
moving the object or load in the direction of the seabed, by means of a first hoisting wire,
exerting a force on the object or load, or on the first hoisting wire, approximately at the bottom end thereof by means of a second hoisting wire and
manipulating the position of the object or the load by means of an apparatus according to one of the preceding claims, the apparatus being attached close to the object or the load. Moreover it is possible that during the deployment of the object or the load, the object or the load is lifted at least partially by means of the secondary hoisting wire.
According to the invention it is possible that during the deployment of the object or the load, the positioning of the apparatus is accomplished using a differential global positioning system (DGPS) navigation system, interfaced with a Hydroacoustic Positioning Reference (HPR) system, a Doppler device and a Fibre Optic Gyro. Moreover it is possible that the apparatus transmits information in the direction of an object on the seabed, in that the apparatus receives a reflection of the signal transmitted to the object, and the reflected information is used to establish the position of the apparatus with respect to the object, and in that the positioning of the load is accomplished by means of a distance log.
According to the present invention it is also possible that
the first hoisting wire is paid out until the first hoisting wire is a least partially lying on the seabed,
hoisting the object or the load and a part of the first hoisting wire by means of the secondary hoisting wire, and
manipulating the position of the object or the load by means of the apparatus.